A new laser Printing technique for the fabrication of thin film transistors
- PDF / 2,392,873 Bytes
- 12 Pages / 390.24 x 621.9 pts Page_size
- 31 Downloads / 179 Views
ABSTRACT We present a new technique for the spatially selective deposition, or "printing", of materials such as Si and Al. This transfer is effected by irradiating a hydrogenated amorphous silicon film deposited on a quartz substrate and coated with the material to be transferred with an excimer laser pulse. The resulting release and accumulation of hydrogen at the film/substrate interface generates pressures sufficient to propel the silicon, as well as any overlying material, onto an adjacent glass receptor wafer. Transient optical transmission measurements performed during the transfer of Si indicate that the amorphous film is melted by the laser pulse and breaks into droplets during ejection. These droplets travel towards the host substrate with a velocity of about 800 m/s and coalesce upon arrival. For fluences above 400 mJ/cm 2, the resulting films adhere well to the receptors and can be smoothed using a second laser irradiation. We fabricated thin film transistors (TFTs) in the printed-and-smoothed Si using conventional lithography. The resulting devices show consistent switching behavior. We have also printed Si and Al lines with widths 5 to 15 Rtm by patterning the laser beam using a reflective grating mask defined on the target substrate. These lines are straight, show few discontinuities, and have sharp edges.
INTRODUCTION There is considerable interest today in the development of direct, spatially selective deposition techniques. These techniques would namely enable the fabrication of semiconductor devices without photolithographic processing, implying a substantial reduction in both the processing time and materials consumption, as well as in the need to use hazardous materials. This is especially relevant for the fabrication of electronic circuits with low device densities, such as the thin film transistor (TFT) arrays used in active matrix liquid crystal displays. Moreover, these techniques are particularly well suited for the fabrication of circuits on non-planar surfaces and other unconventional substrates. In this paper, we present a novel laser-assisted transfer technique based on the explosive release of hydrogen from hydrogenated amorphous silicon (a-Si:H). Our "printing" procedure is well suited for the deposition of silicon, but can also be applied to other materials used in the fabrication of electronic devices, such as Al and Si0 2 . Moreover, it is inherently spatially selective since the dimensions of the transferred features depend on those of the incident laser beam. The use of pulsed laser irradiation to transfer pre-coated layers from a transparent support onto a host substrate was first demonstrated over a decade ago [1]. In that work, ejection of the film from the support was caused by laser-induced evaporation of the film at the film/support interface [2]. Studies on this process have concentrated on the transfer of metals such as tungsten [3] and gold [4], while little attention has been paid to the transfer of semiconductor materials. 213 Mat. Res. Soc. Symp. Proc. Vol. 558 02000
Data Loading...
